Replying to Okay fuck that

when i turn on my computer today i get this antivirus 2008 thing pop up and scans my computer. i figure my dad got it somewhere so i let it do its thing. then it says i have 15 virus things and i need to pay for there registered version. so i just X out of it. now when i go to certain sites it comes up with an error page that says "this website is insecure, your computer is infected with viruses, download antivirus 2008"
then there is a button that says "continue to purchase antivirus protection" and one that says "continue to the desired page" so i click the second, only it doesnt do anything. the link doesnt work.
biggest scam ever. i know nothing about computers how do i get rid of it?